1. Field of the Invention
The present invention relates to an external component for a microprocessor system for a substantially automatic control of one or more control or adjusting elements without burdening the microprocessor system and to a method of operating this sort of external component.
2. Prior Art
It is known to control an electrical control element, such as a magnetic valve, with a microprocessor. The microprocessor transmits control commands according to a predetermined program to the control element via the system bus, which permits a very flexible control of the control element. It is disadvantageous however that the system bus of the microprocessor system is blocked during operation by the transmission of the control commands and thus is not available for other applications. This can lead to time delays when several control elements are under control of the microprocessor, because only one control element can be controlled at a time via the system bus of the microprocessor system.
Thus external intelligent components that can control the individual control elements largely automatically and thus cannot block the system bus of the microprocessor system are increasingly used for time-critical applications. The microprocessor transmits the information that is required for control of the control elements to the external components over the system bus prior to operation of the individual control elements. For example, in the case of a magnetic valve as control element the desired opening and closing times can be transmitted. During operation the control of the control element automatically occurs then according to the information transmitted from the microprocessor system. The system bus of the microprocessor system can then be used for other purposes. In this way it is also possible to control several control elements exactly at the same predetermined time.
The independence of the external intelligent components of course allows an improved control of the control elements, especially in time-critical applications, but this brings up the problem of control of these components by the microprocessor in reliability-critical applications. Thus an incorrect or erroneous operation by one control element cooperating with several control elements usually requires a suitable adjustment of the remaining control elements, which however is difficult because of the decentralized control of the control elements by the external components.
It is an object of the present invention to provide a method of control of several control elements of the above-described kind simultaneously, in which external components generally automatically control the respective control elements in order to reduce the load on the microprocessor system, however sufficient control of the control elements is possible for the purposes of establishing reliability.
It is especially an object of the present invention to provide external components for automatic operation of respective control elements by control commands from a microprocessor system that can be used in a system to provide more reliable control of the control elements.
According to the invention the external component for a microprocessor system for essentially automatic control of a control element without burdening the microprocessor system includes
a data input for receiving a plurality of control parameters for the control element from the microprocessor system;
a data memory connected with the data input for storing the control parameters received from the microprocessor system for subsequent control of the control element;
a controller connected with the data memory for sequential read out of the control parameters stored in the data memory and for sequential control of the control element with the control parameters read out from the data memory;
wherein the controller has at least one control input for affecting read out of the control parameters and control of the control element, the at least one control input is connected with the microprocessor system or one or more additional components in order to facilitate control by the microprocessor system or the additional components.
According to the invention the method of operating the external component for a microprocessor system for substantially automatic control of a control element without burdening the microprocessor system includes the steps of:
a) transmitting a sequence of control parameters for the control element from the microprocessor system into the data memory of the external component;
b) reading out the control parameters from the data memory;
c) controlling the control element according to the control parameters read from the data memory; and
d) transmitting a start signal from the microprocessor system to the external component to establish a safe or reliable state on failure of communication between the microprocessor system and the external components.
The invention includes the disclosure that control of a control element by the associated external component should start only when the microprocessor system transmits a suitable signal to the respective external components. On failure of communication between the microprocessor system and the external component this component is necessarily placed in a safe state. The control process can be started by transmission of a data word from the microprocessor system to the external component or by input of a binary signal.
In an advantageous embodiment of the invention the external component only begins to control of the control element when several control signals produced by the microprocessor system or by other additional external components take predetermined values. For example, it is thus possible that one external intelligent component stops the remaining external components when an incorrect operation of the associated control element is detected, in order to prevent operational difficulties. Also the individual components may be synchronized in this way since a fresh start of the control cycle stored in the external components is initiated when all control elements have finished their predetermined operating cycles and it signals the additional components by means of an appropriate control signal. The individual external components have veto power for control of the remaining external components. The control signals of the individual components are preferably combined by a logical gate. Combination with the control signal of the microprocessor system is also possible. Preferably an or-gate can be used so that each external component alone can block all other components.
The term xe2x80x98control elementxe2x80x99 generally is understood to include all structural elements whose behavior can be directly or indirectly controlled by an electrically input variable.